agate: add page (#6904)

pages/common/agate.md

@@ -0,0 +1,16 @@
+# agate
+
+> A simple server for the Gemini network protocol.
+> More information: <https://github.com/mbrubeck/agate>.
+
+- Run and generate a private key and certificate:
+
+`agate --content {{path/to/content/}} --addr {{[::]:1965}} --addr {{0.0.0.0:1965}} --hostname {{example.com}} --lang {{en-US}}`
+
+- Run server:
+
+`agate {{path/to/file}}`
+
+- Display help:
+
+`agate -h`